view.getViewTreeObserver().addOnGlobalLayoutListener(listener);

public interface OnSoftKeyboardStateChangedListener {
  public void OnSoftKeyboardStateChanged(boolean isKeyBoardShow, int keyboardHeight);
}

//注册软键盘状态变化监听
public void addSoftKeyboardChangedListener(OnSoftKeyboardStateChangedListener listener) {
  if (listener != null) {
    mKeyboardStateListeners.add(listener);
  }
}
//取消软键盘状态变化监听
public void removeSoftKeyboardChangedListener(OnSoftKeyboardStateChangedListener listener) {
  if (listener != null) {
    mKeyboardStateListeners.remove(listener);
  }
}

private ArrayList<OnSoftKeyboardStateChangedListener> mKeyboardStateListeners;   //软键盘状态监听列表
private OnGlobalLayoutListener mLayoutChangeListener;
private boolean mIsSoftKeyboardShowing;

@Override
protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_login);
  mIsSoftKeyboardShowing = false;
  mKeyboardStateListeners = new ArrayList<OnSoftKeyboardStateChangedListener>();
  mLayoutChangeListener = new OnGlobalLayoutListener() {
    @Override
    public void onGlobalLayout() {
      //判断窗口可见区域大小
      Rect r = new Rect();
      getWindow().getDecorView().getWindowVisibleDisplayFrame(r);
      //如果屏幕高度和Window可见区域高度差值大于整个屏幕高度的1/3，则表示软键盘显示中，否则软键盘为隐藏状态。
      int heightDifference = screenHeight - (r.bottom - r.top);
      boolean isKeyboardShowing = heightDifference > screenHeight/3;

      //如果之前软键盘状态为显示，现在为关闭，或者之前为关闭，现在为显示，则表示软键盘的状态发生了改变
      if ((mIsSoftKeyboardShowing && !isKeyboardShowing) || (!mIsSoftKeyboardShowing && isKeyboardShowing)) {
        mIsSoftKeyboardShowing = isKeyboardShowing;
        for (int i = 0; i < mKeyboardStateListeners.size(); i++) {
          OnSoftKeyboardStateChangedListener listener = mKeyboardStateListeners.get(i);
          listener.OnSoftKeyboardStateChanged(mIsSoftKeyboardShowing, heightDifference);
        }
      }
    }
  };
  //注册布局变化监听
  getWindow().getDecorView().getViewTreeObserver().addOnGlobalLayoutListener(mLayoutChangeListener);
}

@SuppressWarnings("deprecation")
@SuppressLint("NewApi")
@Override
protected void onDestroy() {
  //移除布局变化监听
  if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN) {
    getWindow().getDecorView().getViewTreeObserver().removeOnGlobalLayoutListener(mLayoutChangeListener);
  } else {
    getWindow().getDecorView().getViewTreeObserver().removeGlobalOnLayoutListener(mLayoutChangeListener);
  }
  super.onDestroy();
};